1. Field of the Invention
The present invention relates to a link actuating device which is used in a device such as a medical device, an industrial device, or the like which is required to operate in a precise and wide operating range in a three-dimensional space.
2. Description of Related Art
One example of a working device equipped with a parallel link mechanism is disclosed in JP Patent Publication No. 2000-94245, and one example of a link actuating device used in a medical device, an industrial device, or the like is disclosed in U.S. Pat. No. 5,893,296.
In the parallel link mechanism of JP Patent Publication No. 2000-94245, the operating angle of each link is small. Therefore, in order to increase the operating range of the travelling plate, the parallel link mechanism is required to have an increased link length. Accordingly, a problem has been found that the dimensions of the mechanism as a whole increase and the apparatus tends to be bulky in size. Also, if the link length is increased, the rigidity of the mechanism as a whole tends to be lowered. For this reason, there has also been a problem that the weight of a tool mounted on the travelling plate, that is, the weight capacity of the travelling plate, is limited to a small value. For these reasons, it is difficult to use the parallel link mechanism in a medical device or the like which requires the parallel link mechanism to be compact in size and to operate in a precise and wide operating range.
The link actuating device of U.S. Pat. No. 5,893,296 includes three or more trinodal chain link mechanisms, thereby being able to operate in a precise and wide operating range, although the link actuating device is compact in size. However, in the above configuration, since each revolute pair section of the link mechanism oscillates, the lives or life-time of the bearings provided in the revolute pair section may be reduced depending on its operating range.